March 16, 2018

We are living in mobile world and so many people use their mobile phone with charger and power bank in case of urgent charge need. If Abraham Maslow was still alive, most probably he adds phone chargers into “hierarchy of needs.” 🙂 Anyway, couple weeks ago I had to charge my cell phone with its original cable. Cable which comes with original phone was supposed to support fast charging, but I could not manage to charge my phone over 5 hours. This made me wondered why this problem happened. During my investigation with high precision ohm meter with different type of USB cables, I saw huge diversity in therms of DC resistance. As you can see from the USB connector picture, outer two terminals have been designed to carry bus voltage, and they have resistance like every conductor.

This image has obtained from www.wikipedia.org

When I observed this DC resistance difference between USB cables, I decided to build a circuit to test my USB cables. Let’s take a look the cable behaviors.

Fig.1: Regular power bank and tester circuit.

Fig.2

Fig.3

Fig.4

Fig.5: Samsung Note 5 original USB cable.

As you can see from Fig.2 to Fig.5. there are huge amount of difference in terms of DC resistance. You may find the tester circuit as below.

I hope it would help for you to chose decent, low power loss USB cables!